Conventionally, a head-up display device (hereinafter abbreviated as HUD device) configured to display a virtual image visually recognized by an occupant has been known. An HUD device disclosed in Patent Literature 1 includes a projector, a light guide mirror, and a combiner having an image forming reflection surface. The projector projects a display light in the form of a light beam. The light guide mirror has a planar light guide reflection surface that reflects the display light from the projector toward the image forming reflection surface. The image forming reflection surface of the combiner reflects the display light from the light guide mirror.
When the HUD device described above is mounted on an instrument panel of a vehicle, it would be preferable to place the image forming reflection surface of the combiner above an upper surface portion of the instrument panel in consideration of the visibility (for example, movement of a line of sight) of the virtual image.
In addition, as a reflection angle of the display light on the image forming reflection surface of the combiner increases, the virtual image would be distorted asymmetrically vertically, for example. For that reason, it is conceivable to reduce an increase in the reflection angle of the display light on the image forming reflection surface.
However, in the image forming reflection surface of the large-sized light guide mirror as disclosed in Patent Literature 1, since the degree of freedom of placement is low, it would be difficult to reflect the display light toward the image forming reflection surface placed above the upper surface portion while reducing an increase in the reflection angle.